1. Technical Field
This invention relates to an engine driven air conditioning apparatus, and more particularly, to a heat exchanging system for an air conditioning apparatus.
2. Description of the Prior Art
Engine driven air conditioning apparatuses are known in the prior art as shown in FIG. 1. The air conditioning apparatus includes compressor 3 driven by engine 4. Reversing valve 5 is connected between the ports of compressor 3, and controls the direction of flow of the working medium or fluid through the circuit of the air conditioning apparatus. Interior heat exchanges 9a and 9b, are disposed in an enclosed interior environment and are linked to reversing valve 5 through check valves 24c and 24b, respectively, which allow fluid flow from reversing valve 5 to the interior heat exchangers. Check valve 24d and stop valve 25d are disposed in series, and the series is disposed in parallel to check valve 24c, and allows fluid flow from interior exchanger 9a to reversing valve 5 when valve 25d is opened. Similarly, check valve 24a and stop valve 25c are disposed in series, and this series is disposed in parallel to check valve 24b and allows fluid flow from interior exchanger 9b to reversing valve 5 when valve 25c is opened.
Exterior heat exchangers 17a and 17b are disposed in exterior air passages 26a and 26b, and are linked to interior heat exchangers 9a and 9b through further elements of the fluid circuit. Expansion valve 10b and check valve 15b are disposed in parallel and are linked on one side to interior heat exchanger 9b. The other side of the parallel arrangement is linked to stop valve 25a. Similarly, expansion valve 10a and check valve 15a are disposed in parallel and are linked on one side to interior heat exchanger 9a. The other side of this parallel arrangement is linked to stop valve 25b which is disposed in parallel to stop valve 25a. Check valves 15a and 15b allow fluid flow therethrough in a direction from the interior exchangers to stop valves 25b and 25a, and prevent fluid flow in the opposite direction. Fluid flow in the opposite direction occurs through expansion valves 10a and 10b. The other side of stop valves 25a and 25b are jointly linked to one side of arrangement 100 which includes stop valve 25e and expansion valve 14a arranged in series, expansion valve 14b disposed in parallel to the series, and check valve 16 also disposed in parallel to the series and allowing fluid flow therethrough in a direction towards the interior heat exchangers. Check valve 16 prevents fluid flow in the opposite direction. Thus, fluid flow in the opposite direction must occur through expansion valve 14b, and through expansion valve 14a when stop valve 25e is open to allow fluid flow therethrough. The other side of arrangement 100 is linked to exterior heat exchangers 17a and 17b. Finally, exterior exchangers 17a and 17b are linked to reversing valve 5.
When the air conditioning apparatus functions in heating mode, reversing valve 5 assumes the configuration shown in solid line in FIG. 1. Working medium flows from compressor 3, via valve 5 through check valves 24c and 24b to interior heat exchangers 9a and 9b. The compressed working medium condenses in the interior heat exchangers and radiates heat to the enclosed interior environment. The condensed fluid flows through check valves 15a and 15b, bypassing expansion valves 10a and 10b, through stop valves 25b and 25a, to arrangement 100. The fluid flows through expansion valve 14b to exterior heat exchangers 17a and 17b. If the quantity of fluid exceeds the capacity of expansion expansion valve 14b, the fluid flows through expansion valve 14a as well, via stop valve 25e. The working fluid absorbs heat and vaporizes in the exterior heat exchangers. The heated fluid medium flows to reversing valve 5 and back to compressor 3 where it is compressed for further circulation through the apparatus.
When the apparatus functions in the cooling mode, reversing valve 5 assumes the configuration shown in the broken line in FIG. 1. Working medium flows from compressor 3, via valve 5, to exterior heat exchangers 17a and 17b. The working medium condenses in the exterior heat exchangers and releases heat, and flows through check valve 16, bypassing expansion valves 14b and 14a of arrangement 100. The medium flows through parallel stop valves 25a and 25b, and parallel expansion valves 10a and 10b to interior heat exchangers 9a and 9b. The medium absorbs heat and vaporizes in interior heat exchanger 9a and 9b, cooling the enclosed environment, and then flows back to compressor 3 through reversing valve 5 for compression and further circulation.
The apparatus also includes a cooling circuit to cool engine 4. Engine coolant which is used to cool engine 4 circulates through the cooling circuit which includes first pair of radiators 18a and 18b and second pair of radiators 19a and 19b. Coolant is circulated through the cooling circuit by water pump 22 disposed in the circuit between engine 4 and the radiators. Electromagnetic valves 21a and 21b are disposed in parallel between engine 4 and the pairs of radiators. Valve 21a controls fluid flow to first radiators 18a and 18b, and valve 21b controls coolant flow to second radiators 19a and 19b. Radiators 18b and 18a extend substantially adjacent to exterior heat exchangers 17a and 17b in passages 26a and 26b. Fan 23 is disposed generally between and above the exterior heat exchangers to circulate air through passages 26a and 26b in the direction of the arrows. Heat is transferred from radiators 18a and 18b to exterior heat exchangers 17a and 17b due to air flow, and due to conduction. Radiators 19a and 19b are disposed behind a thermally insulating barrier (shown in dashed lines) from the exterior heat exchangers to substantially prevent heat transfer therebetween.
During the heating mode of the apparatus, electromagnetic valve 21a is opened and electromagnetic valve 21b is closed, that is, coolant flows through valve 21a and is prevented from flowing through valve 21b. Thus, heated engine coolant flows through first radiators 18a and 18b located adjacent to exterior heat exchangers 17a and 17b and waste heat from engine 4 is transferred to the working medium circulating through the exterior heat exchangers. The medium absorbs heat and vaporizes. In contrast, when the apparatus is operating in the cooling mode, electromagnetic valve 21a is closed, and electromagnetic valve 21b is opened, allowing fluid flow from engine 4 to second radiators 19a and 19b. Engine heat is not transferred from radiators 19a and 19b to heat exchangers 17a and 17b, and working medium in the exterior heat exchangers radiates heat and condenses during the cooling mode of the apparatus.
The disposition of second radiators 19a and 19b in the cross-sectional area of airflow spaces 26a and 26b, reduces the cross-sectional area of passages 26a and 26b occupied by exterior heat exchangers 17a and 17b. Thus, the heating capacity of the apparatus is not as large as it could be. Furthermore, the provision of both first and second pairs of radiators 18a and 18b, and 19a and 19b complicates the construction of the apparatus and necessitates the additional provision of electromagnetic valves 21a and 21b to control the flow of coolant. Finally, a time delay occurs when electromagnetic valves 21a and 21b are switched, which may result in the blocking of the flow of engine coolant to the radiators for a significant period of time, possibly causing the engine to overheat.